Preparation of liquid-crystal compounds

ABSTRACT

THERE IS DISCLOSED THE PREPARATION OF LIQUID-CRYSTAL COMPOUNDS OF THE STRUCTURE:   1-(C4H9-),4-(CH3-O-(CH2)X-O-(1,4-PHENYLENE)-CH=N-)BENZENE   WHERE X EQUALS 2 TO 10, TYPICALLY 2 TO 5. THE COMPOUNDS ARE PREPARED BY THE REACTION OF PARA-N-BUTYLANILINE AND PARA-METHOXYALKYLENEOXYBENZALDEHYDE.

Sal?

United.

3,751,467 PREPARATION OF LIQUID-CRYSTAL COMPOUNDS Heinz J. Dietrich andEdward L. Steiger, Toledo, Ohio, assignors to Owens-Illinois, Inc. NoDrawing. Filed May 19, 1971, Ser. No. 145,028 Int. Cl. C07c 119/00 US.Cl. 260-566 F 3 Claims ABSTRACT OF THE DISCLOSURE There is disclosed thepreparation of liquid-crystal compounds of the structure:

where x equals 2 to 10, typically 2 to 5. The compounds are prepared bythe reaction of para-n-butylaniline andpara-methoxyalkyleneoxybenzaldehyde.

THE DISCLOSURE where x is 2 to 10, typically 2 to 5, by the reaction ofpara-n-butylaniline,

and para-methoxyalkyleneoxybenzaldehyde,

where x is as defined above.

The para-methoxy-alkyleneoxybenzaldehydes of this invention are preparedby a first reaction of para-hydroxybenzaldehyde and potassium hydroxidein a dimethyl formamide-benzene (1:1) solvent mixture, refluxing atabout 100 C. to remove the water of reaction azeotropically, andreacting the product of the first reaction with an appropriatemethoxyalkyl halide. The solution is then heated to reflux for about 4to 6 hours. After the solvents are removed in vacuum, the products areseparated from the inorganic residues by a water immiscible solventfollowed :by fractionation to recover the requiredpara-methoxy-alkyleneoxybenzaldehyde.

The following equations are representative:

no-ono KOH KO@-OHO The appropriate methoxyalkyl halide is prepared bythe chlorination of a methoxy alcohol, CH O(CH OH where x is as definedabove.

The para-substituted aromatic amines used in this work are commerciallyavailable and may be typically used without further purification.

Schiif bases are prepared by refluxing equimolar quantities of thep-substituted benzaldehyde and aniline in anhydrous ethanol for about 4to 6 hours. The solvent and water are removed and the residuerecrystallized several times from ethanol until the transitiontemperatures remain constant. The crude yields ranged from 70 to Theinfra-red spectra show a strong band at 1629 cm.- corresponding to thecarbon nitrogen double bond in Schilf base compounds. Other absorptionsare compatible with the expected structures.

Transition temperatures are determined on a Leitz Ortholux polarizingmicroscope using a Mettler FP-Z heating stage.

N(para 2 methoxyethoxybenzylidene) para-n-butylaniline (where x is 2 inthe basic structure) was prepared in accordance with this invention. Thestructure was analyzed at 76.84 percent by weight carbon, 8.14 percentby weight hydrogen, and 3.77 percent by weight nitrogen compared withcalculated theoretical analysis values of 77.14 percent by weightcarbon, 8.09 percent by weight hydrogen, and 4.49 percent by weightnitrogen. The compound changed from the crystalline to the nematic phaseat 345 C. and from nematic to isotropic at 56.6 C.

N(para-3 methoxypropoxybenzylidene) para-n-butylaniline (where x is 3 inthe basic structure) was prepared in accordance with this invention. Thestructure was analyzed at 77.16 percent by weight carbon, 8.21 percentby weight hydrogen, and 4.46 percent by weight nitrogen compared withcalculated theoretical analysis values of 77.50 percent by weightcarbon, 8.36 percent by weight hydrogen, and 4.30 percent by weightnitrogen. The compound changed from the crystalline to the nematic phaseat 2.5 C. and from nematic to isotropic at 4.4 C.

The liquid-crystal compounds prepared in accordance with this inventionmay be utilized in display devices, especially of the electronic type.

Such devices typically comprise a thin layer of liquid crystalssandwiched between two sheets of glass. Normally, the thin layer ofliquid-crystal material is clear, but when an electric field is appliedto it, some portions or regions of the material become turbulent so asto scatter light. By controlling the size and shape of the turbulentregions, images can be formed. Primarily, this effect is obtained by useof liquid-crystal materials of the nematic type.

In one particular embodiment, a liquid-crystal material is sandwiched asa dielectric in a parallel plate capacitor with one electrodetransparent and the other electrode either transparent or reflecting.The liquid is kept between the electrodes by capillary action, sinceelectrode spacings are of the order of /2 mil. An applied DC. orlow-frequency (less than Hz). field of more than 30,000 volts percentimeter changes the cell from transparent to turbulent in a fewmilliseconds. Depending upon the liquid-crystal composition, the opaqueeflect may remain even after the field is removed. In other words, anoptical signal may be maintained with no applied power. The cell can beturned clear again by applying a higherfrequency (greater than 700 Hz.)signal. The sample remains clear after the signal is removed.

Additional embodiments of liquid-crystal electrooptical devices aredisclosed and illustrated in US. Letters Pats. 3,401,262 and 3,410,999;Proceedings of the IEEE, vol. 56, No. 12, December 1968, pages 2146 to2149; The Glass Industry, August 1968, pages 423 to 425; Chemical andEngineering News, Sept. 30, 1968, pages 32 and 33;

3 Physics Today, July 1970, pages 30 to 36; Electronics, July 6, 1970,pages 64 to 70; U.S. Letters Patent 3,322,485 to Williams.

It is also contemplated using the liquid-crystal compounds in a chargestorage display-memory device especially multiple gas dischargedisplay/memory panels which have an electrical memory and which arecapable of producing a visual display or representation of data such asnumerals, letters, television display, radar displays, binary words,etc.

Multiple gas discharge display and/or memory panels of the type withwhich the present invention is especially concerned are characterized byan ionizable gaseous medium, usually a mixture of at least two gases atan appropriate gas pressure, in a thin gas chamber or space between apair of opposed dielectric charge storage members which are backed byconductor (electrode) members, the conductor members backing eachdielectric member being transversely oriented to define a plurality ofdiscrete dis charge volumes and constituting a discharge. In some priorart panels the discharge units are additionally defined by surroundingor confining physical structure such as by cells or apertures inperforated glass plates and the like so as to be physically isolatedrelative to other units. In either case, with or without the confiningphysical structure, charges (electrons, ions) produced upon ionizationof the gas of a selected discharge unit, when proper alternatingoperating potentials are applied to selected conductors thereof, arecollected upon the surfaces of the dielectric at specifically definedlocations and constitute an electrical field opposing the electricalfield which created them so as to terminate the discharge for theremainder of the half cycle and aid in the initiation of a discharge ona succeeding opposite half cycle of applied voltage, such charges as arestored constituting an electrical memory.

Thus, the dielectric layers prevent the passage of any conductivecurrent from the conductor members to the gaseous medium and also serveas collecting surfaces for ionized gaseous medium charges (electrons,ions) during the alternate half cycles of the A.C. operating potentials,such charges collecting first on one elemental or discrete dielectricsurface area and then on an opposing elemental or discrete dielectricsurface area on alternate half cycles to constitute an electricalmemory.

An example of a panel structure containing non-physically isolated oropen discharge units is disclosed in U.S. Letters Patent 3,499,168issued to Theodore C. Baker et al.

An example of a panel containing physically isolated units is disclosedin the article by D. L. Bitzer and H. G. Slottow entitled The PlasmaDisplay Panela Digitally Addressable Display With Inherent Memory,Proceeding of the Fall Joint Computer Conference, IEEE, San Francisco,Calif., November 1966, pages 541-547. Also reference is made to US.Letters Patent 3,559,190.

In the operation of the panel, a continuous volume of ionizable gas isconfined between a pair of photoemissive dielectric surfaces backed byconductor arrays forming matrix elements. The cross conductor arrays maybe orthogonally related (but any other configuration of conductor arraysmay be used) to define a plurality of opposed pairs of charge storageareas on the surfaces of the dielectric bounding or confining the gas.Thus, for a conductor matrix having H rows and C columns the number ofelemental discharge volumes will be the product HXC and the number ofelemental or discrete areas will be twice the number of elementaldischarge volumes.

The gas is one which produces light (if visual display is an objective)and a copious supply of charges (ions and electrons) during discharge.In an open cell Baker et al. type panel, the gas pressure and theelectric field are sufficient to laterally confine charges generated ondischarge within elemental or discrete volumes of gas between opposedpairs of elemental or discrete dielectric areas within the perimeter ofsuch areas, especially in a panel containing non-isolated units.

As described in the Baker et al. patent, the space between thedielectric surfaces occupied by the gas is such as to permit photonsgenerated on discharge in a selected discrete or elemental volume of gasto pass freely through the gas space and strike surface areas ofdielectric remote from the selected discrete volumes, such remote,photon struck dielectric surface areas thereby emitting electrons so asto condition other and more remote elemental volumes for discharges at auniform applied potential.

With respect to the memory function of a given discharge panel, theallowable distance or spacing between the dielectric surfaces depends,inter alia, on the frequency of the alternating current supply, thedistance typically being greater for lower frequencies.

In the practice of this invention, it is contemplated that a particularliquid crystal may be prepared and/ or utilized alone or in combinationwith other liquid/crystal compositions of the same or difierent family,e.g. such as a mixture of 2 or more compositions. This may be especiallydesirable since mixtures of compounds may have lower transitiontemperatures than the individual compounds.

We claim:

1. As a composition of matter, a compound having the chemical structurephase at about 34.5% C. and from nematic to isotropic at about 56.6 C.

3. The composition of claim 1 wherein x is 3 and the compound changesfrom the crystalline to the nematic phase at about 2.5 C. and fromnematic to isotropic at about 4.4 C.

References Cited Rudolph Gabler of Leipzig, [Inaugural DissertationKelker et al.: Angewandte Chemie, 22, 903-4 (1969).

Weygand, Z.: Physik. Chemie, vol. 53, pp. -77 (1942).

BERNARD HELFIN, Primary Examiner G. A. SCHWARTZ, Assistant Examiner U.S.ci. X.R. 350 R, 260-600

